1. Field
The present disclosure relates to a light emitting device configured to produce white light or pseudo-white light without using a fluorescent material.
2. Description of the Related Art
Light emitting diodes (LEDs) using semiconductors are a relatively efficient, environmentally-friendly light source and have been used in a variety of fields including displays, optical communications, automobiles, and general lightings. In particular, a demand for white light emitting diodes has been increasing.
To produce white light, a fluorescent material may be used. For example, after an ultraviolet (UV) LED emits an UV ray, red, green, and blue fluorescent materials are excited by the UV ray so as to emit red, green, and blue lights, thereby obtaining the white light. Also, yellow light may be emitted by exciting a yellow fluorescent material that is a complementary color to a blue LED used as a light source so that the white light may be obtained.
As a method of producing a white color by using the LED only and without a fluorescent material, LEDs (each emitting one of red, green, and blue visible rays) are combined. For example, an LED using an InGaN layer as a light emitting material is such that the emitted color varies according to a change in mole fraction of In in the InGaN layer. As the content of In increases, lattice constant increases and a relatively large lattice mismatch is generated between the InGaN layer of a thin layer and a base substrate. Thus, the efficiency in the light emission may be deteriorated from a relatively short wavelength to a relatively long wavelength.